Tissue engineering extends into a diverse range of disciplines that includes chemistry, biology, and engineering. The applications of these principles toward the human body can directly affect the quality of life for people suffering from afflictions as common as osteoarthritis to those as serious as heart disease. The many potential benefits of tissue engineering include the development or revolution of current technology in total hip, knee, cartilage, tendon, and vascular tissue replacement. Many of these practices at present involve implanting either an autologous, allologous, or synthetic graft in place of the damaged area. Within the body, the implant must satisfy requirements pertaining to biocompatibility as well as functional and mechanical stability. Unfortunately, many materials react compatibly with the body but cannot meet the long-term mechanical, geometrical, and functional requirements of the body.
In contrast with many conventional procedures and materials, tissue engineering aims to repair, restore, or regenerate living tissue instead of replacing it with a synthetic implant. One approach to tissue engineering is to provide the body with a basic scaffold that mimics the natural structure of the tissue while providing a temporary functional support. When the appropriate cells are attached to the scaffold, they will proliferate and differentiate into the desired phenotype. If the cells can be culled from the body and propagated in vitro into a viable implant, then the device can be installed in the system and possibly operate as smoothly as healthy tissue. Ideally, the scaffold would then slowly degrade within the body, allowing the body to replace the artificial matrix with a natural one.
Of the types of tissues in the body, the connective tissues seem to offer a great deal of promise for using scaffolds. Examples of connective tissues include ligaments, tendons, cartilage, bone, etc. Without wishing to be bound by a particular theory, it is believed that this is due to the morphology of the connective tissues; the connective tissues comprise cells in various matrices (i.e. semi-solid, solid elastic, and solid rigid). The matrix structure of the connective tissues allows for a scaffold implant to be easily received and incorporated into the tissue.
The first step towards tissue engineering is to characterize the tissue's mechanical, biochemical, structural, and functional properties. Then a search begins for the material or combinations of materials that will meet all the characteristics determined initially. The struggle to find the perfect material often results in weighing the criteria against each other and choosing the most important factors in the success of the implant. For example, in bone repair or replacement the most important function that the implant must perform is to bear the load placed on it by the body over time. The other functions of the bone, such as housing the bone marrow that produces red blood cells, are less important, as long as the rest of the body can make up the red blood cell production. Therefore the preferred materials for bone replacement have traditionally been metals, e.g. titanium, and ceramics, e.g. calcium phosphate ceramics, with high compressive strengths. These traditional materials lack certain desired properties and are therefore not entirely satisfactory.
Because the field of tissue engineering is constantly changing, based on the improved understanding of the body, there remains a need in the art for methods and apparatus to improve tissue stabilization and/or regeneration.